Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque
H, W = map(int, input().split())
S = [input() for i in range(H)]
C = sum(s.count('.') for s in S)

dd = ((-1, 0), (0, -1), (1, 0), (0, 1))
que = deque([(0, 0, 0)])
used = {(0, 0)}

res = None
while que:
    s, t, cost = que.popleft()
    if s == H-1 and t == W-1:
        res = cost
        break
    for di, dj in dd:
        ni = s + di; nj = t + dj
        if (not 0 <= ni < H) or (not 0 <= nj < W) or S[ni][nj] == '#' or (ni, nj) in used:
            continue
        used.add((ni, nj))
        que.append((ni, nj, cost + 1))
if res:
    print(C - 1 - res)
else:
    print(-1)